In case anyone is interested, I've recently rolled in one of those Black Plates 1950s RCA 5R4GY Rectifier with brown base and square getters.

This rectifier tube is readily available for reasonable prices <US$40 from major online tube retailers or around US$20 if you are lucky on e-bay.

1. Inner Resolution

Compared with the Tung Sol 5Y3GT, the extreme inner resolution of the RCA 5R4GY blows the 5Y3GT away.

I can hear the faintest whispers easily in the recording studio or venue for live recordings.

For e.g., the "one, two, three" near the beginning of Brad Paisley's "This is country music" is more distinctive.

It was already present when using a 5Y3GT but I do not have to strain at all to hear the faintest whispers.

BTW, I replaced the Lorenz PCC88 input tube with an Amperex Pinched Waist 6922 for the improvement in midrange and top-end extension.

However, I lost that magical inner resolution of the Lorenz PCC88.

With the 5R4GY, I have gained back the magical extreme inner resolution of the Lorenz PCC88.

If you are the type of audiophile who wants to hear everything in a recording, e.g. the girlish giggling from a member of the audience in one of Brandi Carlile's live recordings, the 5R4GY is highly recommended.

2. Vertical Dimension to Soundstage

Another plus point is that it adds a spatial vertical dimension to recordings.

The CSP2+ already excels in left-right channel separation.

However, when using the 5Y3 family of valves which it was originally designed for, the vertical dimension is not pronounced enough for me.

I vaguely recall Skylab (from Head-Fi) having mentioned this weakness of the CSP2+ when he reviewed it.

After I added the 5R4GY, when I listened to Hotel California by the Eagles, somewhere in the beginning of the track, the sonic "swish"/ "swhosh" sound effect not only appears on the left ( as when using the 5Y3) but now seems to move in a spiral (i.e. with distinctive High-low height) fashion on the left side.

The original vertical sonic dimension weakness appears to have been "fixed" through the use of the 5R4GY.

Interesting. I was using a Phillips 5R4GYS that I got from Upscale Audio a while back that I really enjoyed, then picked up a 1952 RCA 5Y3GT(a pair, actually) which I'm now using. I find that it provides just a bit more in the way of soundstage depth and separation. Really fantastic tube, and personally I like using a tube that the pre was voiced with. That said, I have pretty good luck with just about all recs I've used in the CSP2.

Great. Look forward to hearing your thoughts. Like you I've accumulated a fair amount of rectifiers in searching for the best sound overall, and so when I read a rave from Kevin at Upscale it doesn't take too much convincing for me to jump on it. One of the real good guys in the business who knows what he's talking about. And he's right about the Phillips. Great tube. Just liking the 52 5Y3 a little more in my system.

Sam as I've mentioned elsewhere probably half a dozen times I own three RCA 5Y3GT tubes on hand and one of them, which I got a long time ago, is just amazing in sound, it's from the 'fifties I think, and although I also have the same tube type in examples from Sylvania and GE, that one tube is just the cat's meow in my CSP2 and CSP2+. Wouldn't surprise me if it's a very similar tube to the RCA you're using. I hope that one I have on hand or one I can find sounds as good in my upcoming ZP3.

I`ve been using the Ge 5u4 (`40`s coke bottle, used ) in the ZP3..very nice. Popped in a Phillips Jan 5y3gtwa..ok...more burn in later. Then Lord S`s RCA 5R4GY post. Curious, doesn`t show on the equivalents charts I`ve found, but his link was informative. Found one from reliable dealer I use on eb, £27-$40 . Should be here tomorrow :) . So ty LS. ...Syd

I recently recived a RCA 5y3 similar to Sam's as well an older Tung Sol. Lon, I suspect the warmth that most RCA tubes provide you what you seek, while I suspect Sam likes the more neutral sound that Tung Sols provide?

I think I am in between. Sam and I share the same speakers that can offer the best detail that I have experienced, but one must be careful what you insert with these speakers at the expense of the best analogue sound. My speakers provide a 3D sound in my acoustically treated room much like I hope Lon experiences with his speakers. Visitors to my listening room are looking for the rear speakers that do not exist; I have only stereo. My speakers often surround the listener with sound that seems to be coming from the rear wall, outside the side walls with a deep, tall front soundstage.

I made two changes to stock for the CSP2+. I swapped out the GE 5R4GY that was its shipped Rec and put in a JAN Sylvania 5U4G. Then I swapped the Driver 6N1P for a Genelex Golden Lion 6922. I left the L/R 6N1P's in place. Definite increase in dynamics. Better bass, the HD650's just sing....I have been listening to Al Di Meola for a couple of hours and the speed and clarity of attack on the guitar strings is amazing.

tybee, the one RCA 5Y3GT that has the magic for me it's not the warmth per se but I think the imaging and sound stage accuracy that endears me to it in the CSP2+. It makes every 5U4G tube sound as if it enlarges and stretches the sound in ways that appear unnatural in comparison. And although other RCA and other brand of 5Y3GT I have on hand can match (or exceed) the warmth, they just don't have that "spot on" sound.

But every circuit is different, and the way a tube interacts with a given input tube, and so many factors! Looking forward to this process with the ZP3, mine is on the bench very soon, got an inquiry from Steve as to whether I wanted a white top plate, or what will soon be the standard, a textured black one like those on the new Super Zen; I went with the white to match my Torii Mk II and CSP2+. . . .

I inserted the RCA 5Y3 in my CSP2 and have been listening all morning with a 45 SET amp and I am finding your observations regarding imaging and soundstage accuracy. I guess it's time to give the RCA 5Y3 an extended listen.